In a letter to a London-based Islamic organisation, Nagat Mostafa, 46, said her husband claimed to be the victim of racist bullying and Islamophobia in Belmarsh jail.

Her letter to al-Maqreze Centre for Historical Studies was sent shortly after Hamza – who is fitted with hooks on both hands – underwent surgery in May to remove an inch of bone from his left arm stump, which had become infected.

She wrote: “I would like to bring to your attention the current plight of my husband…

“The reason that his arm needed further amputation was because of the removal of his prostheses, resulting in him constantly putting pressure on the remainder of his fore limbs. As there is no soft furnishing in his cell, he has been suffering considerable pain… After surgery, before he had even recovered from the anaesthetic, he was returned to Belmarsh, only to be told he had to move from his cell to another one. He was so weak and unable to stand that he refused, resulting in him being put in solitary confinement…

“My husband says the racist bullying and Islamophobia against him have intensified.”

The contents of the letter were disclosed by the Maqreze Centre, which called the cleric’s treatment “unjust” and said it feared he could die behind bars.

Ms Mostafa married Hamza in an Islamic ceremony in 1985, a year after he divorced his first wife. The couple have seven children. Hamza, who preached at Finsbury Park mosque, north London, was jailed in 2006 after being convicted of 11 charges of inciting murder and race hate.

An estimated one in six of Belmarsh’s 920 prisoners is Muslim. Prison officers gave warning last week of the threat of extremists “radicalising” inmates.

Steve Gough, the vice-chairman of the Prison Officers’ Association, said: “If you go to Belmarsh you’d see 20 going to Friday prayers a few years ago. Now you’ll see 150.

“Put it this way, we’re a power station and you don’t want us to explode. The radical Muslims make the IRA look like kittens.”